Check the following.
- Check that the computer volume is not muted.
- Check that the wireless speaker you want to connect is set as a playback device.
In the Sound settings of the computer, check that the speaker is set to Default Device.
- Restart the music software.
- Turn off the Bluetooth function of the computer, and then turn it on again.
- Delete the device information from the computer, and then pair with the speaker again.
For details, refer to: How to delete the Bluetooth device information of your playback device
NOTE: Operation is not guaranteed on all computers including self-made computers.